This invention relates in general to ultrasonic measuring equipment and more particularly to a removable-clamp-on ultrasonic transducer for use in measuring fluid characteristics within a conduit. Ultrasonic measurement of the flow of a fluid within a conduit may utilize a variety of methods: contrapropagating transmission (upstream-downstream), reflection or Doppler, interaction with shed vortices, correlation, noise, etc. Many applications require that the transducers be coupled to the exterior of the conduit, without penetrating the wall.
In some cases, for example Doppler methods, only one transducer need be coupled to the pipe. In other cases two or more transducers may need to be coupled to the pipe. The transducers may need to be coupled on opposite sides, on the same side, or, for measurement of swirl, along the pipe at the ends of paths which may be rotated from one another.
Prior art transducer clamps generally consist of some sort of strapping arrangement attached directly to the transducer wedges. For example, hose clamps have been used, encircling both the pipe and the transducer wedge. Equivalently, turnbuckle and cable arrangements have been used. In either case, as the clamping means is tightened, the transducer's position varies, due to motion of the clamp. Prior art clamps do not provide for precise repositioning of the transducer.
Clamp-on ultrasonic transducers are known in the art. In one type of measurement problem it is desired to survey fluid conditions (particularly flow velocity) within different pipes at different locations about a plant using only one measurement device. In other applications the transducers may be considered dedicated to a particular site and will be bonded to the pipe with RTV rubber or epoxy. In the former case it is important that when the transducers are brought back to a particular site, they must be repositioned in the same location, or readings are unlikely to be repeatable despite the same flow velocity. Not only should the location and spacing of the transducers be repeatable, even the coupling conditions, e.g., pressure, should be repeatable, so as to not distort the pipe by different amounts on different occasions. One of these locations may be on a calibration flow loop. In the dedicated case, during the time that the couplant is curing, it is important that the transducers do not move. Furthermore, if dedicated transducers are being applied to two or more pipes whose contents are to be mixed in a controlled manner, e.g. pigments for a paint mixture, then it becomes important that installations on the several pipes are effected in a precise manner.
One problem associated with prior art transducers lies in the adjustment of the pressure between the transducer and the pipe or conduit. In general in the art the same adjustment elements that control the degree of tightness with which the clamp is fastened to the conduit, also controls the contact pressure of the transducing element. Too much pressure damages the element; too little and the clamp may slip either longitudinally or radially.